"Lt. Keenan Kunst at the Royal Air Force station in Lakenheath, Suffolk County, which hosts U.S. Air force units and personnel, said in a telephone interview that the helicopter went down in the coastal village of Cley, near the base. He said the aircraft was based there and on a training mission.

"In Washington, a U.S. defense official said the accident killed the four U.S. Air Force crew members aboard. The official spoke on condition of anonymity because he was not authorized to discuss the crash publicly.

"Police in Norfolk County cordoned off the area where the crash occurred, and several vehicles from the fire brigade, coast guard and police are at the scene."

The BBC reports that the helicopter appeared to have crashed in a nature preserve.

The network quotes an eyewitness saying the helicopter was flying very low. A spokesman for the Royal National Lifeboat Institution said while three lifeboats responded to the scene, the helicopter appears to have crashed on land.